When determining the level of a filling material in a vessel or outside of closed vessels (free field), fill level measuring devices can be used, which emit radar or ultrasonic signals towards the filling material and register the signal reflected at the filling material, in order to ascertain a level therefrom.
In the spectra of the power averaged over time of fill level measuring devices (also termed RMS spectrum (RMS=Root Mean Square)), which emit radar waves, for example, in the form of frequency-modulated continuous wave (FMCW) signals as a transmission signal or measuring signal for measuring the level, power peaks can occur at certain frequencies of the transmission signal. These power peaks can arise due to the transmission signal remaining at a certain frequency.
In the case in particular in which radar waves are used in level measurement, statutory requirements exist with regard to a maximum mean power level of the radiated signal. So as not to exceed permitted transmission levels, to which harmonised standards apply in the EU, for example, the transmission level can generally be kept correspondingly low. Another option for not exceeding permissible limit values for the mean power of a transmission level consists in emitting the radar signals in a clocked manner. In this case, a radar signal is emitted by the fill level measuring device within an active period. An inactive period then follows, within which the fill level measuring device or the radar system of the fill level measuring device that is responsible for generating and emitting the radar signal is switched off. The mean power of the emitted signal can be effectively reduced as a result. However, the peak power of the transmission signal cannot be influenced by this.